Voltammetry on solid electrode - Various electrode configurations

This article focuses on the theoretical description and experimental implementation of solid electrode voltammetry, which can take various forms and configurations. The techniques described aim to meet the growing need to study species with specific spectrophotometric properties, species that are insoluble in common solvents, electrochemical reactions involving very short-lived entities, or electrochemical reactions in vivo or in confined environments. More specifically, this article describes five types of voltammetry.

Thin-film voltammetry involves isolating a very small amount of the electroactive species on the surface of the working electrode, which will participate fully in the electrochemical reaction. Unlike conventional voltammetry [P 2 126] , all of the reagent contained in the thin film is electrolyzed during the plotting of a curve. This thin-film voltammetry is mainly used to study simple charge transfer reactions (e.g., calculation of the number of electrons exchanged) and chemical reactions coupled with charge transfers. It also allows the identification of electroactive intermediate species and the study of their evolution. The creation of an optically transparent thin-film electrochemical cell makes it possible to identify, by spectrophotometry, the species formed at the electrode.

Voltammetry of adsorbed or thin-film electroactive species is particularly relevant in the case of modified electrodes, where the electroactive substance is generally confined within a thin polymer film deposited on the electrode surface. The electrochemical transformation takes place within this thin film (known as a closed system) impregnated with the electrolytic solution.

Voltammetry using a graphite paste electrode allows the electrochemical behavior of electroactive compounds that are strictly insoluble (or very slightly soluble) in common solvents to be studied. In fact, the electrochemical determination of this type of compound faces the experimental problem of establishing effective contact, allowing electron transfer between these compounds, the electrode surface, and the electrolyte solution (triple contact).

Rotating disk and ring electrode voltammetry can be used to study reaction mechanisms and to detect and identify short-lived intermediate species.

Voltammetry using ultramicroelectrodes (micrometric or even nanometric in size) offers numerous advantages, such as reduced non-Faradaic interference...